Do you mean alternator? The thing on the engine that charges the batteries...
Do you mean charger? The thing that takes 120V shorepower and charges the batteries...
Do you really mean inverter? As Tom said, this takes 12V OUT of the batteries and turns it into 120V, and he's right, they pretty much hadn't yet "invented" them for marine use and were never standard items on Catalina yachts, usually being installed either by dealers or owners.